Filtering of Altimetric Sea Surface Heights with a global approach

The geoid models from GRACE and soon GOCE in combination with sea surface geometry data from satellite altimetry allow to obtain a precise estimate of the absolute dynamic sea surface topography with rather high spatial resolution. However, this requires the combination of data with fundamentally different characteristics and different spatial resolutions. One of the central objectives must be to get altimetric data and the geoid spectrally consistent without loss of precision and/or resolution. Therefore it is necessary to find a representation common to the geoid model and to altimetry that allows to obtain spectral consistency by filtering the altimetric data. We try to design a filter for the altimetric data, using the spectral characteristics of the satellite gravimetric geoid, considering a “global” approach. It consists of the extension of the altimetric sea surface height so as to cover all of the Earth's surface and the representation of the data in terms of spherical harmonic functions. The effect of the extension of the data to the land areas is studied in detail.